A truck powertrain comprises an internal combustion engine that drives road-engaging wheels through a drivetrain. The drivetrain comprises a transmission, a driveshaft, and an axle. The engine is coupled to the input of the transmission, through a clutch in the case of a manual transmission, and the driveshaft couples the transmission output shaft to the axle. The driven wheels are mounted at the ends of the axle.
A truck that has a transfer case associated with its transmission can deliver torque through the transfer case to auxiliary equipment. The auxiliary equipment can assume any of various forms. For example, the transfer case may provide output torque at a power take-off, or PTO, that is coupled to a powerconsuming device such as a hydraulic pump.
For any of various reasons, it may be appropriate for auxiliary equipment to be engaged with and disengaged from a transmission via a transfer case only under certain prevailing conditions. Hence, engagement and/or disengagement may be allowed under some conditions and prohibited under others.
One aspect of the present invention relates to a new and unique electric circuit for allowing engagement and/or disengagement of auxiliary equipment with and/or from a transmission via a transfer case under certain defined conditions and disallowing such engagement and/or disengagement under others.
A presently preferred embodiment of the invention employs electric circuit components connected in a new and unique cooperative association to achieve the desired objectives.
A general aspect of the invention relates to: an automotive vehicle that comprises an engine for powering the vehicle, a drivetrain, including a transmission, through which the engine can deliver torque to road-engaging driven wheels for propelling the vehicle, a transfer case associated with the transmission for operating auxiliary equipment, and a system for engaging and disengaging the wheels from the transmission and for engaging and disengaging the auxiliary equipment with and from the transmission through the transfer case.
The system comprises: a first electric-operated device, such as a first solenoid, that is selectively operable to a first state that causes the driven wheels to be engaged with the transmission and to a second state that causes the driven wheels to be disengaged from the transmission; a second electric-operated device, such as a second solenoid, that is selectively operable to a first state that causes the auxiliary equipment to be disengaged from the transmission and to a second state that causes the auxiliary equipment to be engaged with the transmission through the transfer case; a module for controlling the first and second electric-operated devices; a first input to the module for requesting concurrent operation of the first and second electric-operated devices to their respective second states; a second input to the module for signaling transmission output shaft speed; and a third input to the module for signaling full engagement of the auxiliary equipment with the transmission through the transfer case.
The module comprises a circuit that is effective, once the third input has signaled full engagement of the auxiliary equipment with the transmission through the transfer case, to prevent both disengagement of the auxiliary equipment from, and engagement of the driven wheels with, the transmission until the second input signals a speed predetermined to be a speed suitable for allowing both disengagement of the auxiliary equipment from, and engagement of the driven wheels with, the transmission.
Other general aspects of the invention relate to the system control circuit and to the module circuit.
The foregoing, along with further features and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. The disclosure includes drawings, briefly described as follows.